Are you looking at the non-OS or the OS version? . Here's my review of the OS version: http://www.aputure.com/blog/2010/11/24/ ... h-samples/
The non-OS is significantly smaller, and I think it'd be a useful lens to have when you want good range in good light. I also contend that build quality with these lenses is actually quite good (on both versions - even better than the Canon 18-200IS which I also have) I've had mine for almost four years now, knocked it around quite a bit, and it's still going strong. I might take a look at hte 18-250 OS instead just to get a bit more range. Despite the softness at the end of the zoom, I've still been able to get plenty of useable shots, and it's really a fun lens and range to have on your camera all at once.